necessity

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The condition or quality of being necessary.
2. n. Something necessary: The necessities of life include food, clothing, and shelter.
3. n. Something dictated by invariable physical laws.
4. n. The force exerted by circumstance.
5. n. The state or fact of being in need.
6. n. Pressing or urgent need, especially that arising from poverty.
7. idiom. of necessity As an inevitable consequence; necessarily.

Century Dictionary and Cyclopedia

1. n. The condition or quality of being necessary or needful; the mode of being or of truth of that which is necessary; the impossibility of the contrary; the absolute character of a determination or limitation which is not merely without exception, but which would be so in any possible state of things; absolute constraint.
2. n. As applied to the human will, the opposite of liberty. Compulsion physical or, more generally, moral; a stress upon the mind causing a person to do something unwillingly or with extreme reluctance: as, to make a virtue of necessity.
3. n. In philosophy, the inevitable determination of the human will by a motive or other cause. This is only a special use of the word in the free-will dispute. In philosophy generally, by the necessity of a cognition is properly meant a cognized necessity, or universality in reference to possible states of things; although some writers use the word to denote a constraint upon the power of thought.
4. n. A condition requisite for the attainment of any purpose; also, a necessary of life, without which life, or at least the life appropriate to one's station, would be impossible.
5. n. Want of the means of living; lack of the means to live as becomes one's station or is one's habit.
6. n. Extreme need, in general.
7. n. Business; something needful to be done.
8. n. Bad illicit spirit.
9. n. Synonyms Necessity, Need. Necessity is more urgent than need: a merchant may have need of more money in order to the most successful managing of his business; he may have a necessity for more cash in hand to avoid going into bankruptcy.

Wiktionary

1. n. The quality or state of being necessary, unavoidable, or absolutely requisite.
2. n. The condition of being needy or necessitous; pressing need; indigence; want.
3. n. That which is necessary; a requisite; something indispensable.
4. n. That which makes an act or an event unavoidable; irresistible force; overruling power; compulsion, physical or moral; fate; fatality.
5. n. The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism.
6. n. law Greater utilitarian good; used in justification of a criminal act.
7. n. law, in the plural Indispensable requirements (of life).

GNU Webster's 1913

1. n. The quality or state of being necessary, unavoidable, or absolutely requisite; inevitableness; indispensableness.
2. n. The condition of being needy or necessitous; pressing need; indigence; want.
3. n. That which is necessary; a necessary; a requisite; something indispensable; -- often in the plural.
4. n. That which makes an act or an event unavoidable; irresistible force; overruling power; compulsion, physical or moral; fate; fatality.
5. n. (Metaph.) The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism.

WordNet 3.0

1. n. the condition of being essential or indispensable
2. n. anything indispensable